Fetal Development Flashcards
Process of fertilization
Sperm fuse with egg to make ZYGOTE in ampulla
Cell Multiplication to morula
- divid into solid mass BLASTOCYST which is covered in TROPOBLAST and what’s in middle develop into the embryo
- trophoblast develop into outer membrane and turn into placenta * needs to attach to fundus (top of uterus) for
1) richest blood supply
2) thicker lining to protect
3) once delivered placenta is pulled behind causing a wound in muscles are best here to help prevent from bleeding too much (prevent hemorrhage)
Zygote
Totally new genetic material
Sex determine at moment if fertilization
XX- girl
XY- boy
Sperm and oval life span
Sperm survive 72 but live 24
Oval fertile for 24
What happens after implantation in fundus
- secret enzymes to protect self
- chorionic villi expanded out into blood filled endometrium for (02, blood, nutrition, waste) until the placenta & unbilicus is made
- not taking moms blood! Only o2 and nutrition transferred to embryo
Implantation
•The trophoblasts attach to surface of endometrium
–Most frequent site of attachment is fundus
- after fertilization, burrows into uterine lining
- Cells of trophoblast continue to grow down into the endometrium forming fingerlike projections called “chorionic villi”
Cellular Differentiation
What makes all the tissues?
•after fertilization, blastocyst cells differentiate into 3 primary germ layers
- All tissues, organs, and structures will develop from one of these three layers
Development of Embryonic Membranes
Formation of amniotic sac
1) CHORION - outermost
–encloses amnion & embryo
–villi grow into endometrium & form fetal part of placenta
–rest of chorion lose villi except where attached to uterine wall
2) AMNION - inner
–thin, protective membrane
–contains amniotic fluid
–as baby grows, comes in contact with chorion
** Eventually the chorion and the amnion “fuse” to form the amniotic sac
Yolk Sac
- Produces primitive red blood cells during the 1st 6 wks of development until fetal liver takes over
- Soon incorporated into the umbilical cord
Amniotic Fluid
- Functions as cushion to protect FETUS & CORD against injury
- Helps control embryo’s temperature
- Allows symmetrical external growth of embryo
- Prevents adherence of amnion to embryo
- Allows freedom of movement
- Allows umbilical cord to float to prevent compression
- Can analyze to determine fetal health and maturity
Amniotic Fluid levels
How does baby influence levels
•Baby influences volume by swallowing fluid, excreting lung fluid and urine
Amniotic Fluid Index
- Method to evaluate the ‘wellness’ of the baby
- Oligohydramnios (<500 ml)
- Polyhydramnios (>2000 ml)
Umbilical Cord
Vein?
Artery?
•Fuses with fetal portion of placenta to provide circulatory pathway
•ONE VEIN AND TWO ARTERIES
–Vein carries oxygenated blood, arteries carry unoxygenated blood
•Contains special connective tissue called Wharton’s Jelly
Umbilical cord compression
If Baby sits on it and compresses ALL circulation perfusion and O2 is compromise
Placenta
- Means of O2, CO2 and nutrient exchange btw embryonic and maternal circulation
- Begins to function about 3rd week after fertilization
•Two parts
–Maternal portion - red & flesh-like
–Fetal portion - shiny gray
•Eventually form a single layer of cells called the “syncytium” where exchange takes place
–Fetal blood and maternal blood should not mix!!
•Blood flow within the intervillous spaces depends on maternal BP
–Blood flows from area of high pressure to area of low pressure
–Braxton-Hicks enhance circulation
–Labor & High BP decrease circulation
•As placenta “ages”, circulation can decrease
•Fetal RBCs can pass into maternal circulation thru breaks in placental membrane
–RH sensitization
Functions of the Placenta
•Fetal Respiration •Nutrition •Excretion •Protection •Endocrine –Produces human chorionic gonadotropin (hCG), progesterone, estrogen, human placental lactogen (hPL) •Immunity –passive
Identical twin
- Develop from single fertilized ovum
- Of same sex and have same phenotype (appearance)
- Identical twins usually have common placenta
- Number of amnions and chorions present depends on timing of division
Fraternal (dizygotic) twin
–Arise from two separate ova fertilized by two separate spermatozoa
–Two placentas, two chorions, and two amnions
–Sometimes placentas fuse and appear to be one
–May be of same or different sex
Fetal Development (what are the 3 stages)
- Preembryonic: 1st 14 days of development after fertilization
- Embryonic: Day 15 through end of 8th week
- Fetal: End of 8th week until birth
1st Trimester (Wks 1-12)
All major body organs form
brain formed from anterior neural tube
heart beats @ day 28, GI system begins
primitive skeletal shape chambers in heart respiratory system begins ear formation begins liver produces RBCs
All body organs formed
Hear heartbeat on ultrasound and/or doppler
ossification of skeleton begins palate complete in mouth skin pink thyroid hormone present insulin present in pancreas
2nd Trimester (Wks 13-27)
Small body development
& Movement
teeth begin to form meconium begins to collect in intestines kidneys assume shape hair present on scalp, sex determined myelination of spinal cord begins *suck and swallow begins *heartbeat heard by fetoscope *quickening felt
Surfactant production begins
brain appears mature
*respiratory movement begins
makes sucking movements
3rd Trimester (Wk 28 & on)
“Fine detail”
nervous system begins regulation adipose tissue accumulates nails, eyebrows, and eyelids are present eyes are open 👀 earlobes soft with little cartilage 👂🏼 few sole creases Antibodies from mom adequate surfactant vernix in skin folds and lanugo on shoulders earlobes firm sex apparent Weight about 3,000 to 3,600 g (6 lb., 10 oz. to 7 lb., 15 oz.)
When most susceptible to Teratogenesis?
1st 8 weeks (embryonic period) most susceptible to teratogens
Teratogenesis effects depend on
–Maternal and fetal genotype
–Stage of development at exposure
–Dose and duration of exposure of the agent
Teratogenesis mom’s environment
–Nutrition
–Hyperthermia
–Cigarettes
–Substance Abuse
